One of the most persistent and difficult problems associated with the design and proper operation of a digital communication system is the effectiveness of equalization of the communication channel. As a practical matter, virtually every transmission media employed as a communication channel introduces some distortion into the signals travelling through the media. Typically, such distortion is caused by impedance mismatches, imperfect transmission characteristics of the media, or adverse transmission environments. For example, the communication channel commonly used by digital data services (DDS) comprises an unloaded four-wire communication channel that attenuates and band-limits information passing through the channel by an amount that varies depending upon the physical size of the wire, and the length of the communication channel. Accordingly, it is common for DDS receivers to employ some type of equalization in an attempt to counteract the effects of the channel on the received information.
Known equalizers operate based upon a model of the communication channel. Clearly, the better the model, the more effective the equalization. However, since one model may not effectively equalize all communication channels, it is common to adjust the gain and bandwidth performance of the equalizer in a stepwise manner so as to maximize received signal amplitude. Regrettably, this process cannot effectively compensate for all possible channel variations, and may lead to equalizer adjustments that do not optimally receive information from the communication channel. Accordingly, a need exists for a more effective communication channel equalizer and more effective equalization techniques.